1. Field of the Invention
This invention relates to a process for the purification of tissue plasminogen activator (tPA).
More particularly, it relates to a process for the purification of tPA which comprises bringing a crude tPA preparation containing various tPA species of different molecular weights into contact with a cation exchanger in advance and separating tPA having a molecular weight of about 70,000 daltons selectively from the cation exchanger by means of the salt gradient elution method.
2. Description of the Prior Art
No practical processes have yet been known to refine tPA having a desired molecular weight from a culture medium which has cultured tPA-producing cells and thus contained a crude tPA preparation with various tPA species of different molecular weights.
As processes to separate proteins having different molecular weights, it has been known that the gel-filtration process is generally applicable and that cation exchangers are used for the purification of tPA (Japanese Patent Laid Open No. 174727/1985). However, no purification processes have been known at all, which purify and prepare a tPA species of a desired molecular weight by removing other tPA species than that having the particular molecular weight, for example, about 70,000 daltons as in the process of the present invention.